Various heat-developable color photographic materials are known, including a positive type heat-developable color photographic material capable of providing positive or negative images when the original is a positive or negative image, respectively.
These include a system using a dye developing agent and a surface latent image type silver halide emulsion described in JP-A-59-165054 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"); a system using a dye-providing compound which has a reducing property and becomes non-releasible of the dye when it reacts with a silver halide at heating, and a surface latent image type silver halide emulsion described in U.S. Pat. No. 4,503,137; a system using a dye-providing compound releasing a diffusible dye by a remaining reducing agent counter-corresponding to the development of silver halide and a surface latent image type silver halide emulsion, described in U.S. Pat. No. 4,559,290, European Pat. No. 220,746A2, and Kokai Giho 87-6199; and a system using a dye-providing compound releasing or forming a dye corresponding to the development of silver halide and an internal latent image type silver halide emulsion, and reversing at processing with a nucleating agent or light described in JP-A-61-107243, JP-A-62-69265, and JP-A-61-159643.
Such positive type heat developable color photographic materials can be used for various purposes such as the reproduction of black-and-white or color transmission or reflective originals, photographing people or scenes, making computer graphic images such as computer animations and computer art, making medical images for, e.g., a CCD endoscope, a microscope, NMR image diagnosis, supersonic image diagnosis, and making images in the printing field, such as camera-ready art and proofs.
Image-forming processes providing images having good quality using these materials include a process of imagewise forming or releasing diffusible dyes from dye-providing compounds with heat development, and transferring the diffusible dyes onto a dye-fixing element containing a mordant by a solvent such as water, a process of transferring these dyes by a high-boiling organic solvent, a process of transferring these dyes onto a dye-fixing element by a hydrophilic solvent contained in the dye-fixing element, and a process of transferring the dyes onto a dye-fixing element such as a support. In these processes negative dye images or positive dye images from the same original can be desirably obtained by changing the dye-providing compounds or the silver halide emulsions used as described, for example, in U.S. Pat. Nos. 4,463,079, 4,474,867, 4,478,927, 4,507,380, 4,500,626, and 4,483,914, JP-A-58-149046, JP-A-58-149047, JP-A-59-152440, JP-A-59-154445, JP-A-59-165054, JP-A-59-180548, JP-A-59-168439, JP-A-59-174832, JP-A-59-174833, JP-A-59-174834, JP-A-59-174635, and JP-A-61-23245, and EP-A2-210,660 and EP-A2-220,746.
In particular, it has recently been investigated to utilize such a diffusion transfer type heat-developable color photographic material for portrait-containing booklets such as passports and bankbooks. Also, it has further been investigated to use the color photographic material for portrait identity cards (ID cards). These booklets or cards are required t have, in addition to portraits, the names, nationalities, sexes, dates of birth as well as letters, signs and bar codes, of information. In this case, portraits are images of continuous tone and letters, signs, bar bodes, are images of discontinuous tone, i.e., "on-off" images. However, when these continuous tone images and on-off images are exposed on the same heat-developable color photographic material under the same image exposure conditions, one of the continuous tone images and the on-off images formed does not have the image quality required. Accordingly, it is necessary to separately expose for the continuous tone images and the on-off images, which results in increased total processing time and complicated exposure means.
Since these various originals each has its own gradation, it is difficult to attain reproduction faithful to various original images using one kind of positive type heat developable color photographic material. That is, when a positive type heat developable color photographic material used has a hard gradation, it is difficult to reproduce images faithful to an original having soft tone, and when a positive type heat developable color photographic material having soft tone is used, it is difficult to reproduce images faithful to an original having hard tone. Accordingly, for reproduction faithful to a desired original, it is necessary to select a positive type heat developable color photographic material suitable for the gradation of the original, whenever the original is changed.
In the field of conventional silver halide photographic materials which are subjected to wet processing using a developer at about normal temperature, in the case of printing images onto a black-and-white photographic paper from a color negative, a weak overall exposure can be applied to the black-and-white photographic paper before image exposure for softening the gradation of the toe portion (low density portion). However, in the case of color photographic materials, this method of softening gradation by overall exposure is little employed owing to technical difficulties such as the number of processing solutions, and the difficulty of color balance control of three colors.
Also, a process is known of obtaining positive images by imagewise exposing a photographic material using internal latent image type silver halide emulsions and then applying an overall exposure in a state that the development does not substantially proceed. In this process, images are reversed by the overall exposure and the overall exposure is a very large power of gradation change. This system can be realized when the development is performed using a long development bath since in such a case, the overall exposure can be applied for a sufficient time. When the development is performed for a short period of time (in particular, within one minute to 30 seconds), the development starts simultaneously with the immersion of a photographic material in the developer and, thereby, overall exposure in the state that the development does not substantially occur is not possible, which makes it difficult to obtain reversal. In particular, reversal by this system is considered to be more difficult for a heat-developable light-sensitive material which is quickly developed without using a processing solution.
Furthermore, JP-A-58-60739 proposes a system of changing the gradation of reversal images by controlling the amount of light for the overall exposure for the reversal but since the overall exposure for reversal also acts as the exposure for controlling the gradation in the system, there is a problem that the tone reproducibility of positive images is poor.